A synthetic zeolite is crystalline aluminosilicate and has uniform pores of angstrom size due to the crystal structure thereof. By utilizing such characteristics, the synthetic zeolite is being used in the industrial field, as a molecular sieve adsorber that adsorbs only the molecules having a certain size, an adsorptive separating agent that adsorbs the molecules having strong affinity, or a base of a catalyst. The “MTW-type zeolite” as a type of synthetic zeolite is a name that represents the type of a framework structure imparted to a zeolite ZSM-12, and zeolites having the same structure include CZH-5, NU-13, TPZ-12, Theta-3, VS-12, and the like. Currently, the MTW-type zeolite is being used in a large amount in the world as a catalyst in the field of petrochemical industry. The MTW-type zeolite is characterized by having 12-membered one-dimensional pores.
Conventionally, the MTW-type zeolite is produced by only a method of using organic ammonium ions as a structure directing agent (hereinafter, abbreviated to “SDA”). Accordingly, the use of SDA has been considered to be necessary for obtaining the MTW-type zeolite. Moreover, since the synthesized MTW-type zeolite contains the SDA, it has been considered that the MTW-type zeolite is necessarily baked before use so as to remove the SDA.
Various synthesis methods of the MTW-type zeolite have been proposed. As a general method, there is a method of using organic ammonium ions, such as tetraethyl ammonium ion, methyl triethyl ammonium ions, or benzyl triethyl ammonium ions, as SDA. In addition, it is also necessary to add ions of alkaline metals such as sodium or lithium. The method is disclosed in, for example, the following PTLs 1 to 3. According to those methods, an MTW-type zeolite having a ratio of SiO2/Al2O3 of 20 or higher is obtained. However, the SDA is expensive, and sometimes most of the SDA in a mother liquor is decomposed after crystallization of the MTW-type zeolite ends. Furthermore, since the SDA is intermixed with the generated zeolite crystals, the zeolite needs to be baked to remove the SDA if the zeolite is used as an adsorbent or a catalyst. At this time, the exhaust gas thereof is the cause of environmental contamination, and in order to perform detoxifying treatment on the synthesized mother liquor containing a decomposition product of the SDA, a large amount of chemical is required. In this way, the synthesis method of an MTW-type zeolite that uses the SDA costs a lot and causes a heavy environmental load. Accordingly, there is a demand for the realization of a production method not using the SDA and an MTW-type zeolite that is obtained from the production method not using the SDA and basically does not contain the SDA.